Shall the bridge foundation be considered as a dynamic one? Means only 50% of the static capacity of the foundation shall be used for design purposes. Please advise.
The design of a bridge foundation must be adequate for all loads transmitted to it, including seismic. Your question is too generic for me to advise you further.
That's all typical for bridges, but it's still too generic to provide anything to work with.
Bridge design is a specialization of structural engineering. This is likely something you're going to need to hand off to someone with the requisite expertise.